(1) Field of the Invention
This invention relates to a speech analysing device, more particularly to an improvement in an analysing device using a "PARTIAL AUTO-CORRELATION COEFFICIENT." (Hereinafter, this coefficient will be called "PARCOR coefficient" for short and an analysing system using the coefficient, "PARCOR system.")
(2) Description of the Prior Art
About a decade has passed since Itakura and Saitoh devised the PARCOR system speech analysis (Itakura et al., REPORTS OF THE MEETING BY THE ACOUSTICAL SOCIETY OF JAPAN, 1976, October, p. 555). Since the content of this system is well known to those skilled in the art, the explanation of the system is hereby deleted.
As devices for determining the PARCOR coefficient k in this PARCOR system, there have so far been proposed a device which incorporates a mini-computer in the device to determine the coefficient k in accordance with the algorithm given by Itakura and Saitoh, a device which determines the coefficient by a lattice method using a lattice type filter and a correlator disclosed in the abovementioned report, and a device by a modified lattice method proposed by Kobayashi and Yamamoto (Yamamoto et al.; "OPERATION ACCURACY OF MODIFIED LATTICE TYPE PARCOR ANALYSING CIRCUIT," REPORTS OF THE MEETING BY THE ACOUSTICAL SOCIETY OF JAPAN, 1977, April, p. 257), and so forth.
The abovementioned lattice method and modified lattice method are suited for the adaptation to a device because they use simple algorithms, However, since the number of operational steps is large, a hardware construction having high processing capacity is required.
On the other hand, the method proposed by J. Le Roux (J. Le. Roux, "A Fixed Point Computation of Partial Correlation Coefficients," IEEE TRANSACTIONS ON ACOUSTICS SPEECH AND SIGNAL PROCESSING, 1977, June, p. 257-259) has a characterizing feature in that the number of steps to be processed is small and the operation accuracy is high. To this date, however, no method has been developed to realize the abovementioned method using simple hardware capable of processing at a high rate.